Automatic screwdown control



y 7, 1966 N. A. WILSON 3,251 ,207

AUTOMATIC SCREWDOWN CONTROL Filed March 8, 1963 5 Sheets-Sheet 1 y 7, 1966 N. A. WILSON 3,251,207

AUTOMATIC SGREWDOWN CONTROL Filed March '8, 1963 5 Sheets-Sheet 5 Fig.3

9 9 J7 I2 IR J |R 1 5c sc w sc sc IR 7 IR |Ac a 4 |AC V TA TACMIB STAND I z l Es PCL PCL. ES 2 1 G2 70 66 58 PN PN i 56 54 E5 PCL PCL 5 E I P 64 72 ea 60 STAND WORK SIDE DRIVE SIDE INVENTOR/ HoTman H. Wilson BY QM WMW H I Zorneys May 17, 1966 N. A. WILSON 3,251,207

AUTOMATIC SCREWDOWN CONTROL Filed March 8, 1963 5 Sheets-Sheet 5 ll4 I6 TMR TMR Inveniom K03 221418? d1. mo

uittoflaaeys United States Patent 3,251,207 I AUTUMATIC SCREWDOWN CUNTRUL Norman A. Wilson, Westhoro, Mass, assignor to Morgan Construction Company, Worcester, Mass, in corporation of Massachusetts Filed Mar. 8, 1963, Ser. No. 263,783

10 Claims. (Cl. 72-12) This invention relates to rolling mills and more particularly to an improved method of continuously gauging and controlling the cross-sectional dimensions of a plurality of rods or billets as they are rolled in a multi-strand rolling mill. As hereinafter utilized, the term strand may be defined as a plurality of successively aligned roll passes in a rolling mill.

In continuous rolling mills, steel billets are introduced into charging furnaces, heated to 'the correct temperature, and then passed through successive rollers which reduce and reshape the billets to produce rods of the correct size and shape. At the present time, these steps or operating sequences are manually controlled.

Numerous problems occur in the reduction of hot billets to finished rod, an example being the difiiculty encountered in obtaining uniformity in the cross-sectional dimensions of the rods. Although this problem has been solved to the extent that good rod can be produced at a reasonable cost, the quantity of high quality finished product that can be obtained from a given mill continues to depend to a great extent on the experience and ability'of operating personnel.

More particularly, in order to increase the tonnage output, it usually becomes necessary to speed up the mill, making the problems of manual control more difficult. \F or example, although operating personnel usually possess a high degree of skill and experience, they frequently have difficulty in adjusting to further increases in mill speed above those they have encountered in past operations. Failure to adapt to these increased speeds can easily result in numerous or long periods of down time which can quickly cancel the beneficial effects of increased mill speed,

thus causing a reduction rather than increase of tonnage output. Since there is a practical limit to an operators ability to adjust to constantly increasing mill speeds, present day mill operations have in some cases reached their ultimate limit.

In accordance with the present invention, the control of cross-sectional rod dimensions rolled in a rolling mill is accomplished by automatic actuation of power screwdown mechanisms located on selected roll stands through use of auxiliary control systems which make the mill operation substantially continuous and without the need of constant attention by operating personnel. Since the greatest latitude in making changes of cross-sectional dimensions prevails where the sections are the largest, it is more attractive economically to 'apply the control system of the invention to the roughing end of the mill.

Thus, although the system herein chosen for purposes of disclosure will be described with reference to stands 1 and 2, it is not necessarily limited to this use and can also be employed in connection with finishing and intermediate stands. In addition, it should be noted that the system may be used to automate an entire mill.

The present invention provides integrated screwdown control for correction of the following types of off-gauge product variations:

(1) Those variations caused by gradual changes in billet size and temperature as well as by changes in the rolling temperatures and chemical analysis ,of the stock.

(2) Those normal variations caused by the front end of a billet or bar entering a stand and striking the rolls, thus upsetting the steady state conditions of rolling.

(3) Those unusual variations caused by a strand leaving or returning to production and thus upsetting prevailing steady state conditions.

Because the causes of oil gange variations may be so sub-divided, the present system of control may also be described for illustrative purposes as being sub-divided into three control loops or sub-circuits. These sub-circuits each perform functions which are interrelated in the overall control system for continuous control of the rod mill.

At the present time, no system is in use for continuously gauging moving rod at selected points along the pass line luring the rolling operation. Consequently, a considerable period of time may elapse before errors can be detected and the necessary roll adjustments performed.

In the present system, automatic gauging devices such as infrared micrometers are mounted adjacent to the pass line in order to continuously scan across the direction of material flow and generate error signals proportional to and of the same polarity as any deviations from a given dimensional setting. These error signals are then selectively utilized by the above-mentioned sub-circuits to adjust power screwdown mechanisms which are mounted on selected roll stands.

Consequently, through use of the control system of the present invention, it is now possible to automatically correct the roll settings for a variety of operating conditions and thereby maintain l8. more uniform rod gauge for a higher proportion of the total mill output while running the mill at speeds in excess of those now practicable. Several significant advantages flow from this application. An increased tonnage output of quality rod is made possible due to the higher speed of operation and closer gauge control over the entire length of the rod. in addition, the amount of off-gauge product is minimized to a considerable extent due to the ability of the present system to continually gauge a plurality of strands in motion and im mediately react to any error in cross-sectional dimensions or change in strand conditions.

These and other features and objects of the invention will become more apparent as the description proceeds with the aid of the accompanying drawings in which:

FIG. 1 is a block diagram illustrating the complete Gauge Control System for stands 1 and 2 of a four strand rolling mill;

FIG. 2 is a circuit diagram illustrating the means embodied in the instantaneous averaging circuits for instantaneously averaging error signals received from two infrared micrometers and for by-passing this step when only one of the two strands measured by the micrometers is filled;

FIG. 3 is a block diagram illustrating a sub-circuit comprising the Gauging Circuit;

FIG. 4 is a block diagram illustrating a sub-circuit comprising the Front End Compensation Circuit; and

FIG. 5 is a block diagram illustrating a sub-circuit comprising the Empty Pass Compensation Circuit.

To facilitate the description of the present invention, reference will first be made to the drawings illustrating the three individual sub-circuits. However, it should be noted at the outset that when the three sub-circuits are combined as illustrated in FIG. 1, several components are capable of performing multiple functions, thereby eliminating the necessity of duplication in each individual sub-circuit, and the operation of all circuits is interrelated to provide overall control of the entire mill.

As can be seen from a reference to FIG. 3 which is a block diagram of the Gauging Circuit controlling stands 1 and 2 of a four strand mill, the circuit is divided into two parts along the center line of the mill, one part controlling the power screwdown mechanism of the drive side of the mill, the other the power screwdown mechanism of the work side.

Infrared micrometers 2, 4-, 6 and 8 continuously scan moving rods 9 to measure a selected cross-sectional dimension which is representative of the prevailing rod gauge. The micrometers produce error signals proportional to the difference between the prevailing rod gauge and the desired rod gauge. The error signals of infrared micrometers 2 and 4 or 6 and 8 on either side of the pass line are sampled for a predetermined interval by sampling circuits SC-l and SC-2 generally indicated at 10 or SC3 and SC-4 generally indicated at 12. The sampled error signals are then transmitted to instantaneous averaging circuits 14 and 16 where they are averaged to obtain an instantaneous average between each pair of sampled error signals. This instantaneous average is then averaged over the predetermined sampling interval by time averaging circuits 18 and 20 to give a time average value.

Reference will now be made to FIG. 2, a circuit diagram, in order to illustrate the means of instantaneously averaging simultaneous signals from two infrared micrometers and for by-passing this step when only one of the two infrared micrometers is emitting a presence signal. For ease of description, reference will be made only to the control components of the drive side in illustrating the above-mentioned procedure. However, it should be noted that the drive and work sides of the mill are controlled through identical systems. It should also be noted that this circuit diagram will apply to both the Gauging Circuit illustrated in FIG. 3 and the Front End Compensation Circuit illustrated in FIG. 4.

As can be seen in FIG. 2, each infrared micrometer 2 and 4 emits a presence signal and an error signal. The presence signals indicate the absence or presence of a bar in the strand being measured, and the error signals are proportional to the difference between the prevailing rod gauge and the desired rod gauge. When bars are present in both strands, presence signals are emitted which energize coils 22, closing switches 26 and 28. This in turn causes a voltage to be impressed across relay coil 30 resulting in the closing of switch 32. Simultaneously error signals emitted by infrared micrometers 2 and 4 are sampled by sampling circuits SC1 and SC-Z and sampled error signals sent to summer-divider 34 where they are added and the sum multiplied by a fac tor of one-half /2). This operation results in an instantaneous averaging of the two sampled error signals. The instantaneous average is then averaged over the predetermined sampling interval by a time average circuit 18 to obtain a time average value which is then sent on to a proportioning network 54.

When, for example, a bar is missing from the strand being measured by infrared micrometer 2, no presence signal is emitted to energize the coil 22 on this side. Consequently, switch 26 remains open, relay coil 30 is not energized and switch 32 also remains open. However, the presence signal emitted by infrared micrometer 4 results in the closing of switch 36 and the opening of switch 38. Since the lack of a presence signal from infrared micrometer 2 results in the closing'of switch 46) and the opening of switch 48, a voltage is then impressed across relay coil 42 resulting in the closing of switch 44. Consequently, although the error signal from infrared micrometer 4 may not pass through summer-divider 34, it may pass through closed switch 44 and through function point 46 to the time averaging circuit 18. When a bar is present in the strand being measured by infrared micrometer 2 and absent from the strand being measured by infrared micrometer a, a similar procedure takes place. The presence signal emitted by infrared micrometer 2 results in the opening of switch 40 and the closing of switches 26 and 48. The absence of a presence signal from infrared micrometer 4 results in the closing of switch 38 and the opening of switches 28 and 36. In this manner, relay coil 34 is not energized and switch 32 again remains open. However, since both switches 38 and 48 are now closed, a voltage is impressed across relay coil 50 resulting in the closing of switch 52. Consequently, the error signal being produced by infrared micrometer 2 is fed directly through junction point 46 to time averaging circuit 18.

Thus it can be seen that when bars are present in both strands, the error signals emitted by infrared micrometers 2 and 4 are fed through summer-divider 34 and closed switch 32 where they are instantaneously averaged before being sent on to a time averaging circuit 18. When one bar is missing, the need to obtain an instantaneous average is no longer present, and the instantaneous averaging feature of the circuit is by-passed.

After passing through time averaging circuit 18, the average error signal is subsequently transmitted to a proportioning network 54 (see FIG. 3) on the drive side of the mill. It should be noted at this time that a similar proportioning network 56 is positioned on the work side of the mill to receive average error signals from an identical system of components located on the drive side. The proportioning networks 54 and 56 proportion the averaged error signals in a predetermined manner between the respective drive and work sides of stands 1 and 2 and transmit partial correction signals to each pair of error storage circuits 58 and 60 or 62 and 64. The error storage circuits have a stored voltage which is changed by the signal received from the proportioning networks. The change, being proportional to the magnitude and sense of the signal received, is subsequently transmitted to position control loops 66 and 68 or 70 and 72 for corresponding screwdown adjustments. By splitting the required connection between two roll stands instead of performing the entire correction on one stand, seesawing action of the roll is minimized and system response is accelerated. In addition, because roll stands 1 and 2 are driven through gearing from the same motor, their respective roll speeds cannot be independently varied. Control of the screwdowns of only one stand would cause the slip and spread of stock in that stand to change. Changing either slip or spread would cause undesirable changes in the volume rate of flow of stock through a subsequent stand.

Upon receiving a partial correction from the error storage circuits, the position control loops then cause the stand screwdown mechanisms located on either the drive side or the work side to move up or down an amount proportional to the magnitude of the partial correction signal. The direction of movement for the power screwdown is governed by the polarity of the partial correction signal.

With the employment of the gauging circuit as previously described, continuous gauging of moving rod with accompanying instantaneous adjustment of power screwdown mechanisms on either the drive or work sides of selected roll stands enables the mill speed to be increased with a corresponding increase in tonnage of accurately rolled stock.

A second source of off-gauge variations in the crosssectional dimensions of rod being rolled will now be described in connection with the Front End Compensation Circuit illustrated in FIG. 4. As a bar or billet enters a roll stand, it strikes the rolls, upsetting steady state rolling conditions and creating a shock which tends to spread the rolls apart. This in turn results in the rolling of a larger product than desired. To prevent formation of this larger product and to compensate for this spreading action, compensating roll adjustments are performed by the Front End Compensation Circuit, a circuit similar to the Gauging Circuit in that it has separate identical controls-for the drive and work sides of selected mill stands.

As the front end of a bar or billet in any strand passes under the infrared micrometers 2, 4, 6 or 8, error signals which are proportional to the difference between the prevailing bar gauge and the desired bar gauge are relayed for a predetermined interval to instantaneous averaging circuits 74 and 76 by either initial condition correcting circuits ICC-1 and ICC2 indicated generally at 78 or by circuits ICC- 3 and ICC-4 at 80. The averaging circuits 74 and 76 average the error signals from the two strands on their -respective side of the mill (work or drive side) to give an instantaneous average, which is then averaged over the predetermined interval by time averaging circircuits 82 or 84 to give a time average value. The averaged error signal is then transmitted to proportioning networks 86 or 88 which proportion the averaged error signal in a predetermined manner and dispatch a partial error signal to initial condition circuits 90 and 92 or 94 and 96 of each stand, wherein the partial corrections are stored for future use.

Thus it can be seen that this portion of the Front End Compensation Circuit is similar to the Gauging Circuit with the exception that the proportioned error signals are stored within the initial condition circuits 90 and 92 or 94 and 96. It should also be noted that the circuit diagram illustrated in FIG. 2 and previously described in relation to the Gauging Circuit will find similar application in the Front End Compensation Circuit. When only one strand on either side of the mill is present, the instan-.

taneous averaging feature of circuits 74 or 76 will again be bypassed and the individual signal averaged by either time averaging circuit 8 2 or 84 to give a time average value.

The method of releasing the error signals stored within initial condition circuits 90 and 9 2 or 94 and 96 will now be described. Because considerable difficulty is sometimes experienced in inserting a billet into stand 1, its presence is detected at a point following its entrance into stand 1 but prior to its entrance into stand 2 by presence circuits 98, 100, 102 and 104 which emit a presence signal when the front end of the bar appears. The presence signals are then transmitted to delay circuits 106, 108, 110 and 112 which in turn transmit control signals to the remainder of the circuit. One control signal on line 1 is transmitted immediately and triggers error signals stored in either initial condition circuits 92 or 96 in order to provide an immediate correction to the corresponding side of stand 1.

A second delayed control signal on line t triggers error signals stored in either initial condition circuit 99 or 94 as the front end of the bar or billet enters stand 2. The error signals pass through summing points 91, 93, 95 or 97 to activate the position control loops. A third delayed control signal on line t is used to activate the initial condition correctingcircuits 78 or 80/ in order to sample the error signals of the infrared gauges as the front end of the bar or billet passes within view. If the preceding adjustments have been insufiicient, infrared gauges 2, 4, 6 and 8 will emit error signals that will again be averaged and sent on through the proportioning networks to be used in correcting the error signals previously stored in the initial condition circuits 90 and 92 or 94 and 96. In this manner, the Front End Compensation Circuit can perform compensating adjustments as abar or billet enters a roll stand, and in addition is capable of correcting adjustments previously performed in order to produce an ou-gauge product.

During the rolling process, should one or more strands leave production, the forces normally exerted by the rolls on each strand become unbalanced due to the absence of i one strand, thereby upsetting the steady rolling conditions and causing errors in the cross-sectional dimensions of the remaining strands. Although the normally brief interval between bars in any strand causes some variations in the cross-sectional dimensions of the remaining strands, this effect has been ignored due to the difii'culty of adjusting for such brief intervals. However, should a strand remain out of production for a period of time in excess of this normal interval, predetermined adjustments are automatically performed by the Empty Pass Compensation Circuit illustrated in FIG. 5. It should be noted that this 6 circuit differs from the two previously mentioned circuits, since corrections are performed simultaneously on both the work and drive sides of selected mill stands as strands enter and leave production.

Predetermined corrections corresponding to the adjustments necessary to compensate for the prolonged absence of any strand are stored in empty pass compensation circuits 90, 92, 94 and 96 which also serve as initial conditioning circuits with other predetermined corrections set in for use in the Front End Compensation Circuit illustrated in FIG. 4. In general, a different correction will be set into the different empty pass compensation circuits 90, 92, 94 and 96 for each strand and the appropriate set of corrections for both sides of both stands will be selected upon the detection of the absence of any strand. For this purpose, each empty pass compensation circuit has four inputs, one from each delay circuit 122, 124, 126 and 128, to permit a delayed signal from any particular strand to select the set of corrections previously established as required to be made to both sides of both stands for the absence of that particular strand.

Presence circuits 98, 190, 102 and 1M determine the absence or presence of a bar at a location following stand 1 and emit distinguishable signals when the rod is present and when the rod is absent. When a strand drops out of production, a not-present signal is transmitted to timers 114, 116, 118 and 129, each having a timing cycle equal to the normal interval between rods or billets. The timing cycle is started by the appearance of a not-present signal and is stopped by a subsequent presence signal. If the not-present signal exists for a period which exceeds the length of the timing interval of a timer, the timer transmits to delay circuits 122, 124, 126 and 128 a suitable signal for delayed control of the empty pass compensation circuits 9t), 92, 9dand 96. These control signals, after being sutiiciently delayed to allow the remainder of the last bar to clear stand 2, are sent to the Empty Pass Compensation Circuits 92 and 96 of stand 1 and to the Empty Pass Compensation Circuits 9i) and 94 of stand 2. As the signal for a particular strand absent reaches the Empty Pass Compensation Circuits, the predetermined stored corrections for that particular strand are triggered and sent through summing points 91, 93, 95 or 97 to the position control loops on both the work and drive sides of both stands. Through this arrangement, appropriate adjustments for prolonged absences from production of any strand are instituted, thereby eliminating the adverse effects of unbalanced rolling pressure on the remaining strands and resulting in a more uniform product.

- When combined, the three sub-circuits comprise the full Gauge Cont-r01 System as illustrated in FIG. 1. In this combination, duplication of some components is avoided and the control functions are interrelated to be compatible to overall automatic operation. For example, only one position control loop for each power screwdown mechanism is necessary, since each loop is capable handling error signals from a plurality of sources.

The previous description of the various sub-circuits is directly applicable to FIG. 1 and will not be repeated. Each correction signal for the position control loops 66, 6 8, 70 and 72 from the various sub-circuits is applied independently or in combination if coincident in time by virtue of the adding circuits 91, 93, 95 and 97. Thus all control functions are continuously operative to sense the various control conditions and apply the appropriate signals in timed relation to the mill controls to achieve the improved operation previously described.

It should also be noted that one sub-circuit may operate simultaneously with other sub-circuits without interference. For example, should both the Front End Compensation Circuit and the Gauging Circuit on one side of the mill operate simultaneously, it is possible that error signals would be transmitted by initial condition circuits and 92 or 94 and 96 and by the error storage circuits 58 and 69 or 62 and 64. It is also possible that some of these error signals would be positive and some negative. However, since all error signals are received by summing points 91, 93, 95 or 97 and added before being finally transmitted as one error signal to the position control loops, the possibility of interference between the various sub-circuits is eliminated.

With this system of control, the operating speed of the mill is no longer limited to such a great extent by the ability of operating personnel in adapting to increased mill speeds. In addition, the remainder of the mill can be adjusted with greater ease if stock with uniform crosssectional dimensions is produced by stands 1 and 2.

It is my intention to cover all changes and modifications of the example of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

I claim:

1. In a rolling mill, a control system for automatically controlling the cross-sectional dimensions of a plurality of moving rods or billets by performing adjustments to the screw-down mechanisms of a selected roll stand in a multi-strand rolling mill, said system comprising gauge measuring devices positioned adjacent each said strands for continuously gauging the transverse dimensions of moving rods or billets as they leave said roll stand, said measuring devices emitting error signals proportional to the diiference between the prevailing bar gauge and the desired bar gauge, means for averaging the values of said error signals to obtain an averaged error signal for the Work and drive side of said stand, and means responsive to said averaged error signals for adjusting the screwdown mechanisms of said roll stand; means for eliminating errors caused by the entrance of said rods or billets in said roll stand, said means comprising a first set of presence sensing devices for detecting the presence of a rod in a strand and emitting presence signals, means responsive to said presence signals for sensing the entrance of said bar in said stand and performing compensating adjustments on said screwdown mechanisms, said adjustments governed by said averaged error signals; and means for eliminating errors caused by prolonged absences from production of individual strands, said means comprising a second set of presence sensing devices for detecting the prolonged absence of a bar or billet by emitting presence signals, and means responsive to the presence signals of said second set of presence sensing devices for performing predetermined adjustments on said screwdown mechanisms to compensate for errors in bar gauge caused by said prolonged absences.

2. The control system as described in claim 1 wherein said gauge measuring devices are comprised of infrared micrometer gauges.

3. The control system as set forth in claim 1 wherein the magnitude of said predetermined adjustments on said screwdown mechanisms is governed by the particular strand or combination of strands absent from production.

4. In a rolling mill, a control system for automatically controlling the cross-sectional dimensions of a plurality of moving rods or billets by performing adjustments to the screwdown mechanism of selected roll stands in a multistrand rolling mill, said system comprising gauge measuring devices positioned adjacent each said strand for continuously gauging the transverse dimensions of moving rods or billets as they leave said roll stands, said measuring devices emitting error signals proportional to the difference between the prevailing bar gauge and the desired bar gauge, means for averaging the values of said error signals to obtain an average error signal for the work and drive side of said roll stands, means for proportioning said average error signal between said roll stands, and means responsive to said proportioned error signal for adjusting the screwdown mechanisms of each of said roll stands; means for eliminating errors caused by the entrance of said rods or billets in said roll stands, said means comprising a first set of presence sensing devices for detecting the presence of a rod in a strand and emitting presence signals, means responsive to said presence signals for sensing the entrance of said rod in said rod stands in order to perform compensating adjustments on said screwdown mechanism, said adjustments governed by said averaged error signals proportioned between said roll stands; and means for eliminating errors caused by prolonged absences from production of individual strands, said means comprising a second set of presence sensing devices for detecting the prolonged absence of a bar or billet from a strand and emitting presence signals, and means responsive to the presence signals of said second set of presence sensing devices for performing predetermined adjustments on the screwdown mechanisms of said roll stands to compensate for said prolonged absences.

5. The control system as set forth in claim 4 wherein said gauge measuring devices are comprised of infrared micrometer gauges.

6. The control system as set forth in claim 5 wherein said predetermined adjustments applied by said means responsive to the presence signals of said second set of presence sensing devices are varied depending on the particular strand or combination of strands absent from production.

7. In a rolling mill, means for controlling off-gauge variations in the cross-sectional dimensions of a plurality of rods or billets by automatically performing adjustments to the screwdown mechanisms of selected roll stands in a multi-strand rolling mill, said means comprising infrared micrometer gauges positioned adjacent each said strands in order to continuously gauge the cross-sectional dimensions of moving rod contained therein, said gauges producing error signals proportional to the difference between the prevailing bar gauge and the desired bar gauge, means for sampling said error signals for a predetermined interval, means for subsequently averaging the sampled values of said error signals to obtain an averaged error signal for the work and drive side of said mill, means for proportioning said averaged error signals in a predetermined manner between said roll stands, and means responsive to said proportioned error signals for performing adjustments to said screwdown mechanisms.

8. In a multi-strand rolling mill, means for eliminating errors in the cross-sectional dimensions of rods or billets caused by the entrance thereof in roll stands, said means comprising a plurality of infrared micrometer gauges suitably mounted along the pas-s line adjacent each said strand, said gauges producing error signals proportional to the difference between the prevailing bar gauge and the desired bar gauge, means for sampling said error signals as the front end of said bars or billets pass under said infrared gauges, means for averaging said sampled error signals to obtain an averaged error signal for the work and the work and drive side of said mill, means for proportioning said averaged error signals in a predetermined manner between said roll stands, means for storing said proportioned error signals, means for detecting the presence of said bars or billets at a predetermined point along the pass line in order to emit presence signals, said presence signals being delayed and subsequently used to release said previously stored error signals as the bars or billets enter said roll stands, and means responsive to said released error signals for performing adjustments to the screwdown mechanism of said roll stands.

9. In a multistrand rolling mill, means for automatically eliminating errors in the cross-sectional dimensions of rods or billets caused by the prolonged absence from production of individual strands comprising; means for storing predetermined corrections calculated to perform roll adjustment necessary to compensate for said prolonged absences, detection means for emitting a signal when a rod or billet is absent from a strand for a period of time greater than the normal interval between rods or billets, said signal used to release said stored predeter- 0 mined corrections, and means responsive to said released corrections for performing said compensating adjustments to said roll stands.

10. In a multi-strand rolling mill, means for automatically eliminating errors in the cross-sectional dimensions of rods or billet-s caused by the prolonged absence from production of individual strands comprising; means for storing predetermined combinations of correction signals calculated to perform roll adjustments necessary to compensate for said prolonged absences, means for detecting the absence of a rod in a strand for a period of time greater than the normal time interval between rods 0r billets and for emitting a presence signal, said presence signal used to select one of said stored predetermined References (Iited by the Examiner UNITED STATES PATENTS 2,933,956 4/1960 Snow 72l3 2,985,043 5/1961 Roberts 80'33 3,054,310 9/ 1962 Varner 8056 3,100,410 8/1963 Hulls et a1. 80--56 CHAR-LES W. LANHAM, Primary Examiner.

combination of correction signals, said selection governed 15 C. H. HITTSON, Assistant Examiner. 

9. IN A MULTI-STRAND ROLLING MILL, MEANS FOR AUTOMATICALLY ELIMINATING ERRORS IN THE CROSS-SECTIONAL DIMENSIONS OF RODS OR BILLETS CAUSED BY THE PROLONGED ABSENCE FROM PRODUCTION OF INDIVIDUAL STRANDS COMPRISING; MEANS FOR STORING PREDETERMINED CORRECTIONS CALCULATED TO PERFORM ROLL ADJUSTMENT NECESSARY TO COMPENSATE FOR SAID PROLONGED ABSENCES, DETECTION MEANS FOR EMITTING A SIGNAL WHEN A ROD OR BILLET IS ABSENT FROM A STRANG FOR A PERIOD 